It is proposed to study the way in which blood-tissue transport of materials is regulated by the circulatory system, and the way in which control of material transport influences patterns of tissue metabolism and function. Measurements will be made in isolated, blood-circulated skeletal muscles of dogs of transport of oxygen and other substances involved in metabolism, and of inert, diffusible substances of similar physical characteristics. The influence of nervous and hormonal control mechanisms on transport of these substances will be studied by direct experiments. The effects of circulatory shock and other circulatory derangements on transport and metabolism will also be investigated. Attempts will be made to explore the way in which various components of the microcirculatory network contribute to material transport and its control.